DSP-Enabled Radio Astronomy: Towards IIIZW35 Reconquest
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DSP-Enabled Radio Astronomy: Towards IIIZW35 Reconquest Rodolphe Weber Laboratoire d’Electronique, Signaux, Images, Polytech’Orleans, Universit´e d’Orl´eans, 12 rue de Blois, BP 6744, 45067 Orl´eans Cedex 2, France Email: [email protected]
´ Cedric Viou Station de Radioastronomie de Nanc¸ay, Observatoire de Paris, CNRS No. 704, 18330 Nanc¸ay, France Email: [email protected]
´ Coffre Andree Station de Radioastronomie de Nanc¸ay, Observatoire de Paris, CNRS No. 704, 18330 Nanc¸ay, France Email: andree.coff[email protected]
Laurent Denis Station de Radioastronomie de Nanc¸ay, Observatoire de Paris, CNRS No. 704, 18330 Nanc¸ay, France Email: [email protected]
Philippe Zarka LESIA, Observatoire de Paris, CNRS, 5 Place Jules Janssen, 92195 Meudon, France Email: [email protected]
Alain Lecacheux LESIA, Observatoire de Paris, CNRS, 5 Place Jules Janssen, 92195 Meudon, France Email: [email protected] Received 31 January 2004; Revised 24 February 2005 In radio astronomy, the radio spectrum is used to detect weak emission from celestial sources. By spectral averaging, observation noise is reduced and weak sources can be detected. However, more and more observations are polluted by man-made radio frequency interferences (RFI). The impact of these RFIs on power spectral measurement ranges from total saturation to subtle distortions of the data. To some extent, elimination of artefacts can be achieved by blanking polluted channels in real time. With this aim in view, a complete real-time digital system has been implemented on a set of FPGA and DSP. The current functionalities of the digital system have high dynamic range of 70 dB, bandwidth selection facilities ranging from 875 kHz to 14 MHz, high spectral resolution through a polyphase filter bank with up to 8192 channels with 49 152 coefficients and real-time time-frequency blanking with a robust threshold detector. This receiver has been used to reobserve the IIIWZ35 astronomical source which has been scrambled by a strong satellite RFI for several years. Keywords and phrases: digital receiver, filter banks, real-time detection, radio astronomy.
1.
INTRODUCTION
Radio astronomy, in common with many other users of the radio spectrum, has the advantage of a few protected frequency bands. However, most scientific questions find their answers in unprotected bands where radio astronomy is not a primary user. Moreover, even in the protected bands,
out-of-band emission regulations are not always sufficient to prevent the pollution of astronomical primary bands. As a result, an increasing number of observations become unusable (see Figure 1d). In practice, the signals received from astronomical objects are considered as correlated Gaussian noise. From the power spectral shape, some astrophysical information, such
DSP-Enabled Radio Astronomy: Towards IIIZW35 Reconquest
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